08-27-2025, 09:07 PM
The AIB report for the F-35A crash at Eielson AFB in Alaska in January has been released, and it's truly insane. The Mishap Aircraft was #3 of a flight of 4, launching with the callsign YETI, to support a two ship of F-35s flying as CHEVY flight for an Air Combat Maneuvering(ACM) mission. Both YETI and CHEVY flights were delayed in the Tango/Uniform area waiting for other aircraft in their flights to troubleshoot minor issues with their aircraft. They ended up waiting 40 minutes in freezing temperatures before the other aircraft were ready to taxi.
Passing through 275 knots on take off, the "GEAR OVERSPEED" warning annunciated in the cockpit. This is not uncommon, especially at Eielson, and annunciates when the computer predicts the aircraft will exceed 300 knots within three seconds. The MP pulled the nose up, and as he got airborne he pulled the throttle back to keep from a landing gear overspeed. He then made a radio call to the rest of his flight requesting to return to High Key over Eielson to troubleshoot after his nose landing gear didn't retract. High Key is an area for emergency aircraft, or simulate emergencies where they are close enough to the runway that if they lose their engine they can glide to the end of the runway and land. He began talking to the SOF(safety of flight) about a slow gear retraction and open nose gear door. He also reported a nose wheel degrade. His wingman came up and did a BDA assessment of the MA, and reported that the nose gear door was open about 2 inches. The SOF and MP reviewed the PCL (Pilot CheckList) and determined that the next step was to lower the landing gear, using the landing gear handle. The MP reported no light in the landing gear handle, and three green. He then began working the nosewheel steering degrade (NWS DEGD), which cleared when he performed a flight control system engine reset (FCS/ENG RESET). This procedure resets the the FCS and FADEC. His plan was to send his wingman off to join the rest of the flight, and he would stay at High Key to burn off fuel, followed by him landing.
Before he could send his wingman off, the wingman reported that his nose gear was cocked approximately 25 degrees left, and the NWS DEGD reappeared. The MP then suggested a conference hotel, which is a conference call between the SOF and Lockheed Martin to discuss something that isn't covered in the PCL. While waiting for the conference hotel, the MP initiated a series of s-turns up to 2.5Gs, as well as a slip maneuver to attempt to realign the nose gear.
Once the conference hotel began, five Lockheed engineers, including a senior software engineer, flight safety engineer, and three LG engineers. They requested status of the aircraft ranging from fuel state, to health codes displayed but never asked where the aircraft was, or what the ambient temperature was at the time this was going on. The SOF informed the MP that the engineers were looking towards a safe answer, which would be an approach end arrestment with the cable. The MP replied that would require a three point attitude, which includes the nose gear on the runway. The engineers believed that the nose wheel centering cam was jammed, but didn't know the cause.
A course of action was decided on where the MP would perform a touch and go with the main wheels, and see if the weight on wheels switch would straighten out the nose wheel. The pilot performed a main landing gear touch and go, and reported that his only status change was an FCS fault that was now "latched" and couldn't be cleared by performing an FCS/ENG RESET. He also reported new HRCs to the SOF to relay to the LM engineers, relating to the left and right main WOW switches that appeared after the touch and go. This is when it starts to go off the rails.
The SOF relayed "some landing gear HRCs", including "a main landing gear HRC or two". The LM engineers wanted to know about the NLG HRC and weren't concerned about the others. The SOF couldn't recall if all five HRCs were reported verbatim, or were simply communicated. The FCS FAULT was related to the RMLG WoW switch 1 and 2 failure. The MP didn't have any indication of why the FCS FAULT advisory was active, or any indication on his HMD or PCD. He again attempted an FCS/ENG RESET, but the fault persisted indicating it was still active.
Neither the MP or the MW were aware that the right main didn't fully extend. There was no visual indication, and only the HRCs recording of the two WOW failures showed that it hadn't. The MW TFLIR recorded both the nose gear turned 20 degrees, and the RMLG not being fully extended. The plan relayed to the MP was to perform a second touch and go, this time lowering the nose gear to the runway to try to align the nose wheel. The aircraft touched down, and the nose wheel went from 20 degrees to 6 degrees. The pilot activated maximum afterburner and lifted off the runway again. Approximately 8 seconds later, the pilot selected FCS/ENG RESET again, and the aircraft almost immediately began to experience pitch and yaw oscillations. The MP attempted to counter the oscillations using the control stick, then entered a left bank. The aircraft immediately rolled hard left and pitched up. At the time of ejection the aircraft showed a 30-40 degree pitch up, -38 degree roll, and 3Gs. After ejection the aircraft continued an upward trajectory, reaching an altitude of 3200 feet before stalling and descending to the ground, where it impacted.
On January 25, to comply with a required 200 hour inspection, a Landing Gear Fluid Servicing maintenance action was completed. This is completed by draining pneumatic pressure and flushing the hydraulic fluid from the landing gear, opening a swivel nut and draining nitrogen and hydraulic fluid from the strut until no air bubbles are seen. At that point pneumatic servicing is performed with the nitrogen cart. A normal servicing requires more than 2 gallons of hydraulic fluid to service all three landing gear. On this servicing, the maintenance crew reported that they used no more than 2 gallons of fluid for the complete servicing. The team only used one hand cart and didn't refill it during servicing.
Following the accident the AFRL recovered hydraulic fluid in the NLG and RMLG and tested it. They found that approximately 1/3rd of the fluid was water. The NLG had 1L of water in 2.8L of recovered fluid, while the RMLG was 1.5L in 4L recovered. The hydraulic fluid was sourced from a barrel from the 355th FGS. Both the barrel and servicing cart were tested using a Portable Oil Diagnostics System(PODS), and the fluid was found to have 1024 ppm particulates, which is more than double the allowable limit. The test system only goes up to 1024 ppm, so it's possible the contamination was even higher than that. The 355th HAZMAT program suffered insufficient manning and frequent supervision changes prior to the accident, and at the time of the accident there was no primary HAZMAT program manager assigned. HACOM managers did not lock the barrels, observe servicing of the carts, log what barrels were used to fill carts, and the pump that was mounted on top of the barrel had no Teflon thread sealer, which would have allowed water to leak into the barrel if it wasn't stored properly.
It was also found that there was insufficient tracking of what barrels went on movements and were returned to Eielson. It's not required to track those movements closely, but there was a barrel that the 354th took to Kadena that was left outside in the rain, but the records were overwritten by a subsequent deployment, so it's not known where that barrel traveled after the deployment. It's not known if that barrel was used to service the MA, and at least one barrel was marked "Empty/Consumed" in April 2024, but wasn't disposed of, and instead was in use at the 355th. Upon testing, the barrel of hydraulic fluid was found to be 33% water.
On Feb 6, 2025 another aircraft took off, and reported an unsafe nose wheel indication. The pilot flew for approximately 40 minutes, before landing safely. Upon inspection the uplock roller was missing causing the NLG to turn 10 degrees left, similar to the accident aircraft. At touchdown the wheel went from 10 degrees to 5 degrees. The aircraft was towed into a climate controlled hangar (70 degrees), and pneumatic pressures were measured. The aircraft was then towed outside, where temperatures remained below 15 degrees. After 12 hours the aircraft was jacked up so all three gear cleared the ground, and measurements of the struts were taken. All three struts were showing partly retracted. Temperatures of the struts were showing as 14 on the NLG, and 7 on both mains. The aircraft was then taken back into a climate controlled hangar and allowed to sit for 12 hours, and the hydraulic fluid was drained from all three landing gear. The nose and left main had a significant amount of water in the hydraulic fluid, while the right main appeared to be all hydraulic fluid. Both aircraft flew missions between landing gear servicing and their respective incidents, but neither spent extended time in freezing conditions before those flights. The temperatures on those days weren't as cold as on their incident days.
Passing through 275 knots on take off, the "GEAR OVERSPEED" warning annunciated in the cockpit. This is not uncommon, especially at Eielson, and annunciates when the computer predicts the aircraft will exceed 300 knots within three seconds. The MP pulled the nose up, and as he got airborne he pulled the throttle back to keep from a landing gear overspeed. He then made a radio call to the rest of his flight requesting to return to High Key over Eielson to troubleshoot after his nose landing gear didn't retract. High Key is an area for emergency aircraft, or simulate emergencies where they are close enough to the runway that if they lose their engine they can glide to the end of the runway and land. He began talking to the SOF(safety of flight) about a slow gear retraction and open nose gear door. He also reported a nose wheel degrade. His wingman came up and did a BDA assessment of the MA, and reported that the nose gear door was open about 2 inches. The SOF and MP reviewed the PCL (Pilot CheckList) and determined that the next step was to lower the landing gear, using the landing gear handle. The MP reported no light in the landing gear handle, and three green. He then began working the nosewheel steering degrade (NWS DEGD), which cleared when he performed a flight control system engine reset (FCS/ENG RESET). This procedure resets the the FCS and FADEC. His plan was to send his wingman off to join the rest of the flight, and he would stay at High Key to burn off fuel, followed by him landing.
Before he could send his wingman off, the wingman reported that his nose gear was cocked approximately 25 degrees left, and the NWS DEGD reappeared. The MP then suggested a conference hotel, which is a conference call between the SOF and Lockheed Martin to discuss something that isn't covered in the PCL. While waiting for the conference hotel, the MP initiated a series of s-turns up to 2.5Gs, as well as a slip maneuver to attempt to realign the nose gear.
Once the conference hotel began, five Lockheed engineers, including a senior software engineer, flight safety engineer, and three LG engineers. They requested status of the aircraft ranging from fuel state, to health codes displayed but never asked where the aircraft was, or what the ambient temperature was at the time this was going on. The SOF informed the MP that the engineers were looking towards a safe answer, which would be an approach end arrestment with the cable. The MP replied that would require a three point attitude, which includes the nose gear on the runway. The engineers believed that the nose wheel centering cam was jammed, but didn't know the cause.
A course of action was decided on where the MP would perform a touch and go with the main wheels, and see if the weight on wheels switch would straighten out the nose wheel. The pilot performed a main landing gear touch and go, and reported that his only status change was an FCS fault that was now "latched" and couldn't be cleared by performing an FCS/ENG RESET. He also reported new HRCs to the SOF to relay to the LM engineers, relating to the left and right main WOW switches that appeared after the touch and go. This is when it starts to go off the rails.
The SOF relayed "some landing gear HRCs", including "a main landing gear HRC or two". The LM engineers wanted to know about the NLG HRC and weren't concerned about the others. The SOF couldn't recall if all five HRCs were reported verbatim, or were simply communicated. The FCS FAULT was related to the RMLG WoW switch 1 and 2 failure. The MP didn't have any indication of why the FCS FAULT advisory was active, or any indication on his HMD or PCD. He again attempted an FCS/ENG RESET, but the fault persisted indicating it was still active.
Neither the MP or the MW were aware that the right main didn't fully extend. There was no visual indication, and only the HRCs recording of the two WOW failures showed that it hadn't. The MW TFLIR recorded both the nose gear turned 20 degrees, and the RMLG not being fully extended. The plan relayed to the MP was to perform a second touch and go, this time lowering the nose gear to the runway to try to align the nose wheel. The aircraft touched down, and the nose wheel went from 20 degrees to 6 degrees. The pilot activated maximum afterburner and lifted off the runway again. Approximately 8 seconds later, the pilot selected FCS/ENG RESET again, and the aircraft almost immediately began to experience pitch and yaw oscillations. The MP attempted to counter the oscillations using the control stick, then entered a left bank. The aircraft immediately rolled hard left and pitched up. At the time of ejection the aircraft showed a 30-40 degree pitch up, -38 degree roll, and 3Gs. After ejection the aircraft continued an upward trajectory, reaching an altitude of 3200 feet before stalling and descending to the ground, where it impacted.
On January 25, to comply with a required 200 hour inspection, a Landing Gear Fluid Servicing maintenance action was completed. This is completed by draining pneumatic pressure and flushing the hydraulic fluid from the landing gear, opening a swivel nut and draining nitrogen and hydraulic fluid from the strut until no air bubbles are seen. At that point pneumatic servicing is performed with the nitrogen cart. A normal servicing requires more than 2 gallons of hydraulic fluid to service all three landing gear. On this servicing, the maintenance crew reported that they used no more than 2 gallons of fluid for the complete servicing. The team only used one hand cart and didn't refill it during servicing.
Following the accident the AFRL recovered hydraulic fluid in the NLG and RMLG and tested it. They found that approximately 1/3rd of the fluid was water. The NLG had 1L of water in 2.8L of recovered fluid, while the RMLG was 1.5L in 4L recovered. The hydraulic fluid was sourced from a barrel from the 355th FGS. Both the barrel and servicing cart were tested using a Portable Oil Diagnostics System(PODS), and the fluid was found to have 1024 ppm particulates, which is more than double the allowable limit. The test system only goes up to 1024 ppm, so it's possible the contamination was even higher than that. The 355th HAZMAT program suffered insufficient manning and frequent supervision changes prior to the accident, and at the time of the accident there was no primary HAZMAT program manager assigned. HACOM managers did not lock the barrels, observe servicing of the carts, log what barrels were used to fill carts, and the pump that was mounted on top of the barrel had no Teflon thread sealer, which would have allowed water to leak into the barrel if it wasn't stored properly.
It was also found that there was insufficient tracking of what barrels went on movements and were returned to Eielson. It's not required to track those movements closely, but there was a barrel that the 354th took to Kadena that was left outside in the rain, but the records were overwritten by a subsequent deployment, so it's not known where that barrel traveled after the deployment. It's not known if that barrel was used to service the MA, and at least one barrel was marked "Empty/Consumed" in April 2024, but wasn't disposed of, and instead was in use at the 355th. Upon testing, the barrel of hydraulic fluid was found to be 33% water.
On Feb 6, 2025 another aircraft took off, and reported an unsafe nose wheel indication. The pilot flew for approximately 40 minutes, before landing safely. Upon inspection the uplock roller was missing causing the NLG to turn 10 degrees left, similar to the accident aircraft. At touchdown the wheel went from 10 degrees to 5 degrees. The aircraft was towed into a climate controlled hangar (70 degrees), and pneumatic pressures were measured. The aircraft was then towed outside, where temperatures remained below 15 degrees. After 12 hours the aircraft was jacked up so all three gear cleared the ground, and measurements of the struts were taken. All three struts were showing partly retracted. Temperatures of the struts were showing as 14 on the NLG, and 7 on both mains. The aircraft was then taken back into a climate controlled hangar and allowed to sit for 12 hours, and the hydraulic fluid was drained from all three landing gear. The nose and left main had a significant amount of water in the hydraulic fluid, while the right main appeared to be all hydraulic fluid. Both aircraft flew missions between landing gear servicing and their respective incidents, but neither spent extended time in freezing conditions before those flights. The temperatures on those days weren't as cold as on their incident days.
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